1. Field of the Invention
The present invention is directed to a liquid crystal cell and the method of making it, which cell has two carrier plates which are spaced from one another by an interposed frame and which have inner surfaces facing each other provided with electrically conductive coatings and preferably covered by insulating layers with at least one electrically conductive coating on one of the two carrier plates being an electrode which is connected to a terminal electrode disposed on the other plate by a conductor bridge which is disposed on the outside of the frame and contains at least one metallizing layer.
2. Prior Art
Liquid crystal cells, which have conductive coatings on the inner surfaces of the carrier plates, which are spaced apart by a frame and which have at least one of the conductive coatings forming electrode which is connected by a contact bridge to a terminal electrode on the other surface, are disclosed in British Patent No. 1,381,429, which corresponds to German Offenlegungsschrift No. 23 33 206 and in British Patent No. 1,478,327, which corresponds to German Offenlegungsschrift No. 23 50 000.
A drive component of a liquid crystal cell can most easily be contacted by arranging all the cell terminals on one of the carrier plates as disclosed in U.S. Pat. No. 3,947,090, which corresponds to German Offenlegungsschrift No. 22 40 781. Therefore, in virtually all of the liquid crystal displays, the electrodes on one carrier plate are connected to the opposite carrier plate. In fact, generally, the rear electrode is connected to a terminal electrode in the plane of the front or segmented electrode on the front carrier plate when taken from the view of the observer. To form this contact, a contact or conductive bridge, which must overcome a distance of approximately 10 .mu.m, must provide a permanently good contact and must be producible without any particular outlay and in particular without any manual operative steps.
For some years, technology has endeavored to produce a through contact which is suitable for mass production, and to this end technology has produced widely different concepts for making these contacts. For example, it has been proposed that the electrode, which is to be lead across, and its terminal electrode should lead out from the end face of their respective carrier plates and thus be bent outward and extend around and onto the edge of the carrier plates and then be connected to one another by a metallization layer (see for example, British Pat. No. 1,381,429). However, as disclosed in British Pat. No. 1,478,327, a reliable contact can be established in this way only if the portion of the electrode, which portion bends around the edge of the carrier plate and which portion is subjected to considerable heat stresses during the subsequent securing of the frame, consist of a different material than the conductive coatings on the surface of the carrier plate and is, for example, aluminum, and if a further solid conductor component is added to the metallization. It is obvious that a conductor bridge designed in this manner will involve considerable production expenses and will necessitate special additional provisions in particular if the carrier plates are to be coated with an insulating layer. Consequently, the present practice is still to employ makeshift measures in which the conductive bridge is manually applied to the exterior of the finished cell as disclosed in Tobias, International Handbook of Liquid Crystal Displays, Ovum Press Limited, 1975, Section 7.3.5.